He took one with characters from the film Frozen rather than one with Marvel superheroes at the Sainsbury's Local store in Anlaby near Hull.

His mother Charlotte Houghton said she was left embarrassed when the cashier told the youngster: "You've got a girls one."

I was mumbling on because I felt guilty, like I was doing something wrong, then I thought, 'What am I doing? Why am I trying to explain? It's got nothing to do with her'Charlotte Houghton

Mrs Houghton said: "I've heard of comments being made to parents before but this was the first time I've personally experienced gender shaming.

"I was really taken aback by it. I then found myself explaining to her - while she was beeping the other items through - that he likes the Frozen one and he always chooses it because of the figures, so that is what he is getting.

"I was mumbling on because I felt guilty, like I was doing something wrong, then I thought, 'What am I doing? Why am I trying to explain? It's got nothing to do with her'."

She added: "I'm sure she meant no harm by her comments but I can't understand this divide of boys and girls toys.

"Personally I think we should encourage our children to play with any toys that they want, as long as they're safe."

The pink Frozen Kinder Surprise Egg contains the characters from the popular film, Anna, Elsa and Olaf.

Mrs Houghton, a location agent from Hull, said she always encourages children Oliver, 10, and Mason to play with toys of their choice.

She said: "If he had wanted a pram I would have let him have one, it wouldn't make him any less of a boy. We've got a kitchen at home and they like playing with the trolleys.

"I just found it really bizarre that she thought it was OK to comment and say that to my son - it has nothing to do with her.

"If it had been a new mum who was upset by it, it could have really knocked their confidence and made them question themselves."

Mrs Houghton posted the incident in the Hull Mummy Friends group on Facebook.

Ferrero, the Italian company that produces the Kinder eggs, said they were not meant to be gender-specific.

A spokeswoman said: "The Frozen Kinder Surprise egg is part of the Pink and Blue range, which offers different branded toy ranges in pink or blue-coloured eggs.

"The Frozen egg is pink. However, Ferrero doesn't advocate or promote Kinder Pink and Blue as a gender-specific product and they are not labelled for girls or boys.

"Kinder Surprise pink and blue eggs help parents navigate the toy ranges on offer and make purchasing decisions based on what is most relevant for their child, as an individual. Feedback from parents shows that they welcome this approach."

Sainsbury's said it was investigating the incident but needed more information before it could comment properly.

A spokeswoman said: "We would encourage Charlotte to contact us directly so we can get to the bottom of what happened."